Known is a technique for forming a thermal spray coating by spraying molten metal onto a cylinder-bore inner surface in a cylinder block of an internal combustion engine. Adherence of the thermal spray coating onto the cylinder-bore inner surface can be strengthened by roughening the cylinder-bore inner surface before forming the thermal spray coating.
Japanese Unexamined Patent Publication No. 2007-211307 discloses a surface roughening work of a cylinder-bore inner surface. In the surface roughening work, a helical groove is formed on the inner surface by use of a cutting tool. By such a surface roughening work by use of a cutting tool, it becomes possible to strengthen adherence of a thermal spray coating more than by other surface roughening works such as shot-blasting. In addition, it also discloses that a horning work is done as a finishing work for a spray-coated surface.